Southern Regional Water Program

Research, Extension & Education Water Quality Programs through the Land Grant University System

Hypoxia

Hypoxia means an absence of oxygen reaching living tissues. Waters with inadequate levels of dissolved oxygen (less than 2 mg/l) to support fish and other aquatic species are called hypoxic. Eutrophic ("rich food") conditions created by the overabundance of nutrients, such as nitrogen, phosphorus, and organic matter, cause hypoxia. Excess nutrients may come from a wide range of sources: runoff from undeveloped and developed land, atmospheric deposition, soil erosion, and agricultural fertilizers. Sewage, urban storm water and industrial discharges also contribute nutrients. Hypoxia is an increasing problem worldwide. Hypoxic zones are found near Denmark, Norway, and Sweden in the Baltic Sea; in the Chesapeake Bay; in the northern Gulf of Mexico; and in Long Island Sound.

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The extent of the dead zone in summer 2001 in the Gulf of Mexico off the coasts of Louisiana and Texas surpassed the previous 1999 record. The hypoxic zone also extended into Texas waters in 2001 and was over four times as large as the hypoxic zone in 2000. The causes of this year-to-year fluctuation in the size of the hypoxic zone are not fully understood.

The United States Environmental Protection Agency (EPA), together with senior representatives from federal, state, and tribal agencies and organizations, formed the Mississippi River/Gulf of Mexico Watershed Nutrient Task Force in 1997. The Task Force was established to study the causes and effects of excessive nutrient runoff to the Mississippi River Basin and to coordinate and implement nutrient reduction activities to alleviate hypoxia in the Gulf of Mexico.

The following agencies maintain web sites that post information regarding current efforts to alleviate hypoxia in the Gulf of Mexico.

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